[SteveRB]

So, i took the leap and added a second eminence 15a to the proven formula. I have a couple questions before i post my results.

1. adding a second driver in series changes the overall load of the speaker system. What could i assume the total load is for the amp? (i am running an old Eico 81 - three output options: 4, 8, or 16ohm)

2. adding a second woofer changes the response of the cross over circuit. what value inductor coil will get me back to a 270hz crossover point?

3. wings? i want to try a couple U and H frame wings. I have read the quarter wave papers which makes me think the length of the wings has an 'optimal' depth.
What would be a good starting point?
In an H frame, does the front and back have to be the same length to be 'optimal'?

any help is appreciated. I plan to post pics and basic test results of the different scenarios for reference.

[opnly bafld]

Series will be @ 16 ohms and parallel will be @ 4 ohms.

Series will raise x-o to @ 2x current and parallel will lower to @ 1/2.

Generally speaking the higher the x-o the less deep the cavity.
http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf

Lin

[Russell Dawkins]

there are some handy aids here - just plug in the impedance and crossover frequency:
http://www.bcae1.com/passxovr.htm

[FullRangeMan]

So, i took the leap and added a second eminence 15a to the proven formula. I have a couple questions before i post my results.

1. adding a second driver in series changes the overall load of the speaker system. What could i assume the total load is for the amp? (i am running an old Eico 81 - three output options: 4, 8, or 16ohm)

2. adding a second woofer changes the response of the cross over circuit. what value inductor coil will get me back to a 270hz crossover point?

3. wings? i want to try a couple U and H frame wings. I have read the quarter wave papers which makes me think the length of the wings has an 'optimal' depth.
What would be a good starting point?
In an H frame, does the front and back have to be the same length to be 'optimal'?

any help is appreciated. I plan to post pics and basic test results of the different scenarios for reference.

Hi all,
This is a interesting thread, as two woofers looks better than one(maybe).
So I also wish to know the inductor value, AWG and type recommended (air core, graphite, coil, Toroidal etc...).
Many Thanks, Gustavo

[SteveRB]

...just got the second pair of Alphas, and roughed them in to the baffle.

wow.

these are great.

going to need a bit of fine tuning, but they sound really good.

(photos and experiments to come)

[Luigi]

I can understand how a pair each side might be pretty darn awesome, but Im thinking the baffle must start to look pretty sizeable as well.

What Im considering is to double up on the B200s, which is where all the main goodness comes from anyway.

I guess people have tried this; I note some don't bother with the Alphas and just do line arrays with four or eight per side.

So any comments from those who might have tried either?

Im kind of more tempted by B200 route as the Alphas have filled in the midbass nicely.

Then again, I should probably direct funds to a NAKSA instead.........decisions, decisions

[aquapiranha]

So, i took the leap and added a second eminence 15a to the proven formula. I have a couple questions before i post my results.

1. adding a second driver in series changes the overall load of the speaker system. What could i assume the total load is for the amp? (i am running an old Eico 81 - three output options: 4, 8, or 16ohm)

2. adding a second woofer changes the response of the cross over circuit. what value inductor coil will get me back to a 270hz crossover point?

3. wings? i want to try a couple U and H frame wings. I have read the quarter wave papers which makes me think the length of the wings has an 'optimal' depth.
What would be a good starting point?
In an H frame, does the front and back have to be the same length to be 'optimal'?

any help is appreciated. I plan to post pics and basic test results of the different scenarios for reference.

I will be interested in your findings. I have the B200 / 2  x Alpha set up now, and I am driving them actively. However, no matter what I do, I just can't get any decent bass out of them! You would have thought that 4 x 15" drivers would = decent bass! but for some reason I just can't do it. I am thinking of scrapping them and going in another direction.

[canzld]

Hi Aquapiranha

My experience with a b200/1x 15a setup is that the amp used to drive the combo is the most important contributor to bass response. Some give good bass- others don't. What amp are using?  My Trends TA-10.1 integrated drives my OB extremely well, but I got a much better bass with Trends pre-power combo - while a much more powerful solid state Cyrus amp gave less. I have noticed many people use a tube amp with good bass results.

[aquapiranha]

Hi Aquapiranha

My experience with a b200/1x 15a setup is that the amp used to drive the combo is the most important contributor to bass response. Some give good bass- others don't. What amp are using?  My Trends TA-10.1 integrated drives my OB extremely well, but I got a much better bass with Trends pre-power combo - while a much more powerful solid state Cyrus amp gave less. I have noticed many people use a tube amp with good bass results.

hi, and thanks for the response. I have tried quite a few different amps and I am currently using a four channel tripath amp. I have used hypex and a couple of others together with a coupl eof valve amps and nothing delivers. Don't get me wrong here I am not a bass freak, but there is simply not enough output from the lower registers no matter what I try. I am considering selling off the drivers and starting again, maybe with a small TL or similar.

Steve

[Russell Dawkins]

Hi Aquapiranha

My experience with a b200/1x 15a setup is that the amp used to drive the combo is the most important contributor to bass response. Some give good bass- others don't. What amp are using?  My Trends TA-10.1 integrated drives my OB extremely well, but I got a much better bass with Trends pre-power combo - while a much more powerful solid state Cyrus amp gave less. I have noticed many people use a tube amp with good bass results.

Amplifier damping factor could be at play here. Higher damping factor contributes to tighter control of the driver and reduces ringing  (shortens "settling time"). Slow settling time is audible in the bass ranges as warmth or, if excessive, as bloat or boominess.

[canzld]

absolutely - with tube amps generally having lowering damping than SS - not sure about T-amp  -somewhere in between perhaps. Perhaps Aquapiranha might want to try boxing (open back) the woofer(s) and leaving the B200 as OB only before venturing to transmission line.

[SteveRB]

I am running an old Eico HF-81 tube amp with the combo. I am not missing any bass from the music: ran the gambit from folk, modern rock, electronic, and hip-hop.

There is a real natural 'punch' to the hip-hop kick drum and a fullness to the rock.

Using the exact same set-up for a DVD there is a lack of 'cinema-bass': the super rumble that only a sub-woofer system reproduces.

I am very happy with the set-up as is -- i wanted to spend a bit more time with it before i really give my opinion and start to try U-Baffles and cross-over points.

I can see myself living with these speakers for a long time.

[Luigi]

Aquapiranha
Like others here, Im finding the Alphas really do dramatically enhance the bass output of the B200s.

Wondering two things about your system; how close are the Alphas to the floor? Mine are virtually on the ground, only an inch or so above it, and are even vulnerable to wagging dog tails - will have to clip their tails I think! Evidently floor proximity has a big effect on bass response in these OB systems.

I find that for music an outboard subwoofer doesn't really enhance things much; there's enough bass from the B200s and Alphas, and it is really clean too.

I notice you have tried many different amps. The other thing that can make a difference is the type of preamp you use. The LDR-based preamps seem to get the very best out of power amps they're well mated to, providing you use an active buffer and/orthe source is well matched to the preamp. And the preamp to the power amp, regarding impedances.

Im only going to four Alphas because the darned things are so cheap. And I have lots of spare wood hanging around.

[canzld]

So I also wish to know the inductor value, AWG and type recommended (air core, graphite, coil, Toroidal etc...).
Many Thanks, Gustavo

I use solid core  http://www.erseaudio.com/Products/SuperQCoils
mainly because I'd seen a few comments saying air core is not the  best for this application and they're cheaper    - haven't tried other kinds to give  you any kind of  comparison
with as low AWG as available and low DCR
exact value will, as stated, above depend upon on how you hook em up.